Subcutaneous insulin administration involves depositing exogenous hormone into the adipose tissue to regulate glycemic levels. Absorption rates fluctuate based on regional vascularity and heat, with the goal of mimicking endogenous basal-bolus patterns. Localized lipohypertrophy results from failure to rotate injection sites within the selected anatomical region. A. Arms: The posterior aspect of the upper arm provides a subcutaneous layer for hormone absorption. This site exhibits a moderate uptake velocity, slower than the trunk but faster than the lower extremities. Physical activity involving the upper limbs can inadvertently accelerate absorption through increased local muscular blood flow. B. Thighs: The anterior and lateral aspects of the thighs serve as common injection points for long-acting analogs. This region possesses the slowest absorption rate due to lower capillary density compared to the trunk. Vigorous exercise significantly alters the pharmacokinetics of insulin deposited in the femoral subcutaneous tissues. C. Abdomen: The abdominal wall is the preferred anatomical site due to the most rapid and consistent pharmacokinetic absorption profile. It provides a large surface area for systematic rotation, minimizing the risk of tissue fibrosis. This site ensures predictable peak action times for preprandial short-acting insulin dosages. D. Upper buttock: The gluteal region offers a thick adipose layer suitable for subcutaneous injections in many patients. Absorption from this site is relatively slow and sustained, similar to the thigh. It is often used for pediatric or lean patients but lacks the rapid uptake required for pre-breakfast insulin.